MERCURY

World at the Edge of the Sun

Mercury is a
small world (4878 km in diameter) only 40 percent larger than our Moon.
It orbits close to the Sun, a third closer than Earth and speeds through
a year in just over 87 days. Mercury spins slowly on its axis, taking 58.6
days to turn once.

Mercury has a surprising
temperature range of -173 to 430 C. It also has a very high density of
5.44 g/cm3. It is not a world we would want to visit, nor one where life
could be expected to survive.